Expand admin SSH command capabilities

Add per-session history, tab completion, interactive prompts, and
bounded input handling. Support deferred lifecycle and host-key actions
after output drains, and document the expanded administration workflow.

src/console_completion.h

@@ -2,6 +2,9 @@
 
 #pragma once
 
+#include <stdbool.h>
+#include <stddef.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -9,6 +12,9 @@ extern "C" {
 /* Install late-terminal upgrade handling and project-specific completion. */
 void console_completion_install(void);
 
+/* Bounded longest-prefix completion shared by the UART and admin SSH frontends. */
+bool console_completion_expand(const char *line, char *completed, size_t capacity);
+
 #ifdef __cplusplus
 }
 #endif